1. Field of the Invention
The present invention relates to a control apparatus of an on-vehicle dynamo-electric machine that is mounted on a vehicle to act as a starter-motor at the time of starting an internal combustion engine and as a generator after starting the internal combustion engine. The invention also relates to a control method of the on-vehicle dynamo-electric machine.
2. Description of the Related Art
In an internal combustion engine mounted on a vehicle, it is often required to reduce number of parts mounted on the internal combustion engine and secure a space enough for an engine room. For that requirement, a motor dynamo (hereinafter referred to as dynamo-electric machine) capable of acting both as a starter-motor for starting the internal combustion engine and as a generator for charging batteries may be used. Dynamo-electric machines for use in vehicles may be classified into two types. One is a dynamo-electric machine that is employed in so-called hybrid vehicles and is directly coupled with a crankshaft of an internal combustion engine to act for starting the internal combustion engine and driving the vehicle, as disclosed in the Japanese Patent Laid-Open (unexamined) No. 140004/1997. Another is a dynamo-electric machine having only the function of starting the internal combustion engine, as disclosed in the Japanese Patent Laid-Open (unexamined) No. 247857/1995. From the viewpoint of securing a space enough for the engine room, the latter having only the starting function is generally employed, and in which case the internal combustion engine and the dynamo-electric machine are connected via any belt or chain and put on practical use.
In such dynamo-electric machine, a three-phase synchronous motor and a generator are usually employed. In case of using the dynamo-electric machine as a motor, power is supplied from an on-vehicle battery via an inverter. In the inverter, transistors (IGBT) or the like are usually used as switching elements. The switching elements are connected in the form of a three-phase bridge and controlled by PWM signal or the like, thus supplying a three-phase ac to the dynamo-electric machine. Diodes are inverse-parallel connected to each switching element to form a rectifier circuit as disclosed in the mentioned the Japanese Patent Laid-Open (unexamined) No. 140004/1997. In case of using the dynamo-electric machine as a generator, the output power of the generator is rectified by the rectifier circuit and charges the batteries.
In the mentioned prior art, in the case of using the dynamo-electric machine as a motor, the switching elements are controlled by PWM signal to supply the dynamo-electric machine with an ac power. On the other hand, in the case of using the dynamo-electric machine as a generator, field currents are controlled to use the dynamo-electric machine as a generator of a constant voltage. It is to be noted that in the mentioned conventional arrangement, both characteristics as a motor and as a generator are low as compared with an arrangement in which a starter-motor and a charging generator are separately disposed. In the technical field of synchronous generator, a technique for controlling a generated voltage is known, in which a generated voltage is controlled by applying a phase controlled compensation current from an inverter to an armature coil. Application of such a control technique to an on-vehicle dynamo-electric machine may be certainly effective from the viewpoint of improving the performance at a low speed. However, the on-vehicle dynamo-electric machine is operated over a wide range of rotation in actual use, and therefore there arise various disadvantages in employing the mentioned control technique.
For example, it is herein supposed that a mode for generating a power by applying a phase-controlled compensation current from an inverter to an armature coil is referred to as xe2x80x9cinverter generation modexe2x80x9d. In the case that such an inverter generation mode is applied to an on-vehicle dynamo-electric machine, when the generated voltage of the armature coil comes up to a certain level, the application of the compensation current becomes impossible due to increase in rotation speed. Eventually, voltage control falls within a state of incapability. Moreover, because the on-vehicle dynamo-electric machine is used while the rotation speed being increased by the internal combustion engine, the voltage control becomes incapable in the range of relatively low rotation speed.
The present invention was made to solve the above-discussed problems and has an object of providing a control apparatus and a control method of an on-vehicle dynamo-electric machine, in which a function as a starter-motor and a function as a charging generator can be both efficiently controlled by shifting from the inverter generation mode to the normal generation in response to the rotation speed of the dynamo-electric machine and eliminating troubles incidental to such shift.
To accomplish the foregoing object, a control apparatus of an on-vehicle dynamo-electric machine according to the invention includes: an armature coil and a field coil; a dynamo-electric machine for acting as a starter-motor and as a charging generator that is combined with an on-vehicle internal combustion engine; switching elements that are bridge connected; an inverter for supplying an ac to the armature coil of the dynamo-electric machine; a field current control means for controlling a current of the field coil; and control means for applying a PWM signal to the switching elements of the inverter and controlling the a current supplied to the field coil. In case that the dynamo-electric machine acts as a charging generator, when a rotation speed of the dynamo-electric machine is not higher than a predetermined value, the control means generates power by applying a compensation current for phase control from the inverter to the armature coil. On the other hand, when a rotation speed of the dynamo-electric machine is not lower than a predetermined value, the control means stops the operation of the inverter. Thus, controlling the current applied to the field coil by the field coil current control means generates a predetermined target voltage.
As a result of such arrangement, it is now possible to obtain an output power from the dynamo-electric machine enough to cover a wide rotation range from a low-speed rotation range to a high-speed rotation range, making it possible to carry out smoothly charging the battery.
A method of controlling an on-vehicle dynamo-electric machine according to the invention is to control an on-vehicle dynamo-electric machine being mounted on an internal combustion engine for vehicles, acting as a starter-motor at the time of starting the internal combustion engine and as a charging generator after starting the internal combustion engine. In case that the dynamo-electric machine acts as a charging generator, a target voltage is generated by controlling a field current under normal operating condition. On the other hand, under the conditions that engine speed of the internal combustion engine is lowered and a voltage generated by the dynamo-electric machine does not reach the target voltage, a power is generated by applying a compensation current for phase control from on-vehicle batteries to an armature coil of the dynamo-electric machine via an inverter.
As a result, it is possible to achieve a control method of an on-vehicle dynamo-electric machine capable of extracting an output power from the dynamo-electric machine enough to cover a wide rotation range from a low-speed rotation range to a high-speed rotation range.
Other objects, features and advantages of the invention will become apparent in the course of the following description with reference to the accompanying drawings.